I slept on my back w/ leg up & bent @ the knee. I tried 2 put leg straight & it made a wet/crunchy pop. Pain & little swelling now. What wrong? T.Y

Can be meniscus. Could of have problem with meniscus, stay off your feet, apply ice, take otc ibuprofen, if pain not better in a few days go get an x-ray, might need physical therapy and MRI eventually.
Joint aligment issue. Probable you hip, knee and leg are out of alignment. That will put pressure on the knee bursaes and they will swell. Treat with heat, epsom soaking, stretching. I use acupuncture! think muscles and tendons and not the joint proper.